Aqueous cleaning compositions that are formulated for removing fatty soils from a variety of substrates have been developed and have been used for many years. A large variety of different types of formulations have been developed to remove fat containing soils from a variety of surfaces.
One type of cleaner for fatty soil are highly alkaline institutional cleaners that chemically saponify fats and remove the saponification reaction products which are more water soluble than the fat precursor. These materials operate using strong bases such as a sodium or potassium hydroxide or silicate in combination with other soil suspending and removing compositions. Other types have included active enzyme compositions which act to remove fat from a substrate by the natural action of the enzyme in breaking the fat down into its constituent substances which can be removed by surfactants or other components in a formulated cleaner. Desirable cleaners, however, remove both protein and fat containing soils.
Proteins are by far the most difficult soils to remove in the food industry and others. In fact, casein (a major milk protein) is used for its adhesive properties in many glues and paints. Food proteins range from simple proteins, which are easier to remove, to more complex proteins, which are very difficult to remove. Heat-denatured proteins can be extremely difficult as they create a protein film which makes the proteins especially difficult for cleaners to reach. Protein soils from milk, eggs, meat etc., can be solubilized by alkaline solutions. Proteins hydrate and swell when they come into contact with water which helps alkalis to react with them, forming soluble salts.
Generally, a highly alkaline detergent with peptizing or dissolving properties is required to remove protein soils. Wetting agents can also be used to increase the wettability and suspendability of proteins. Protein films, which tend to be created at higher temperatures when proteins become denatured, require alkaline cleaners which have hypochlorite in addition to wetting agents. Chlorine is typically employed to degrade protein by oxidative cleavage and hydrolysis of the peptide bond, which breaks apart large protein molecules into smaller peptide chains. The conformational structure of the protein disintegrates, dramatically lowering the binding energies, and effecting desorption from the surface, followed by solubilization or suspension into the cleaning solution.
Temperature is extremely significant in cleaning operations. Too high of a temperature can cause excess denaturing of proteins and the creation of protein films which are difficult to remove. In general, however, increasing the temperature decreases the strength of bonds between the soil and the surface, decreases viscosity and increases turbulent action, increases the solubility of soluble materials, and increases chemical reaction rates. Higher temperatures are generally beneficial, as long as they are not so high as to cause protein denaturation. Higher temperatures are also costly to employ and difficult to maintain consistently.
A balance must be struck between higher temperature with increased soil removal efficiency and the higher cost and difficulties of maintaining the same. Cleaning methods differ with respect to whether the soil is cleaned in an automated (clean-in-place or CIP) process or manually. Automated cleaning can be done safely at temperatures up to or exceeding (under high pressure) the boiling point of water. Cleaning solutions as well as final rinse water can be heated to facilitate soil removal and equipment surfaces holding the food soil are heated as well, also facilitating the cleaning process. As automated systems can recirculate cleaning solution, the mechanical solution flow supports the removal of soil. In addition, the ability to re-heat the cleaning solution, by passing it through a heat exchanger during the cleaning operation, supports the removal of soil by keeping the equipment surfaces at a constant and high cleaning temperature.
For manual cleaning operations, especially in open, large facility environments, cleaning does not generally benefit by heating the chemical cleaning solution as the large surface areas to be cleaned will rapidly cool the solution to ambient temperature. In such cleaning operations, chemical residence time on a surface (often in the form of foam or a gel, especially for vertical surfaces) and high temperature rinse water is required to effectively clean a surface. Unfortunately for these types of manual cleaning operations, rinse water temperature is usually limited at the high end to between 120° F. and 140° F. for employee safety reasons. Without the ability to recirculate the hot water, as is common in automated operations, a much higher amount of water is required to heat up a soiled surface for these environmental areas and the costs of heating cold water to these temperatures can be significant.
As can be seen, there is a need in the art for alkaline cleaning compositions that can clean these environmental surfaces and remove proteins and fats at lower temperatures (i.e. less than 120° F.) and even as low as 50° F. without a decrease in cleaning performance.